Improving the Design of a Heat Exchanger using SOLIDWORKS Flow Simulation
• # Improving the Design of a Heat Exchanger using SOLIDWORKS Flow Simulation

Heat Exchangers are important devices when we need to remove heat from a temperature sensitive area. You can find this in automation systems, locomotives, air-conditioning and many more. A typical heat exchanger looks like this:

But it comes in many shapes and sizes, like these:

Basically a heat exchanger can be defined as a device that is used to transfer heat between one or more mediums. As such, the efficiency of a heat exchange is thus its ability to channel heat energy from one area to another. There are many factors that could affect the efficiency, such as the material of the solid (metals being good conductor makes them ideal), the coolant fluid (fluid that can contain higher amounts of energy is preferred), the fluid path (larger surface area means larger area for heat dissipation), and so on.

With so many variables in play, it may be difficult to decide what is the best design for a particular heat transfer scenario. This is where computational fluid dynamics (CFD) analysis comes in.

The heat exchanger below contains HOT water on the inside, with COLD water on the outside acting as the coolant. There are a few channels on the inside containing the HOT water, which is being surrounded by the COLD water in the cavity:

For this scenario, I would like to see if a concurrent flow or a parallel flow would cool the HOT water the most. A concurrent flow is whereby the HOT and COLD water inlets are on opposite sides, and parallel flow is whereby the HOT and COLD water inlets are on the same side:

I will fix the following variables in this scenario:

Flow Rate of inlet COLD Water: 0.0005 m^3/s

Flow Rate of inlet HOT Water: 0.0002 m^3/s

Solid Material: Copper

Before we go into the results, lets see what is the best way to calculate the efficiency of the heat exchanger. The idea is to be able to transfer all the heat energy from the hot water to the cold water. That means the heat energy lost by the HOT water equals the heat energy gained by the COLD water. Mathematically that would be:

Using SOLIDWORKS Flow Simulation, we have the ability to expand the capabilities of the CFD analysis by adding additional equation in terms of equation goal, allowing us to immediately find the results for the efficiency.

Now that we have created the scenario and set-up in SOLIDWORKS Flow Simulation, all we need to do is run the study and obtain the results:

Parallel Flow

Concurrent Flow

From this analysis we see that the Parallel flow is more efficient in cooling the HOT water, making it the more obvious choice. But what comes next?

Usually in designing a heat exchanger, the designer would know what is the amount of heat energy or what the final temperature of the HOT liquid should be at the end of the process. As mentioned, the designer would need to consider:

1. The necessary flow rate needed to achieve this, so that the right pump can be chosen to achieve that flow rate
2. The necessary coolant to achieve the goal, allowing the ability to choose cheaper coolants
3. The necessary fluid channels in the heat exchanger, allowing the designer to optimize the material and manufacturing cost.